Ok so 13.5 is 3500kv which the G2 3300kv will be the closest. 10.5 is 4500kv. The G2 SCT 4000kv or the G2 4100kv will be the closest. The max10 G2 is 80a ESC. The SCT version is 140a ESC. Both are sensored. If you are doing both racing and bashing then the G2 or a castle sensored combo will be the best. If you are strictly doing racing with the slash then a more competitive hobbywing system or tekin system will do the job. But fkr bashing and racing, any of the max10 G2 will be best. With the max10 all the wires comes ready to go. With more competitive systems and castle systems you would need to solder battery connector and motor wires which idk if you can solder. So imo the G2 will be the best. Now tires. Look for SCT carpet tires. I would talk to the guys that run there about the tires and compounds. Another thing I would do to the car is try to get the car lower for better handling. Idk about your track but at my old LHS I took corners way to fast and traction rolled so I would try to take corners a little bit slow at first then get faster. Also another thing to note if you go and race like every other weekend the slash will be alright. If you race more and more I would suggest to get a more competitive sct kit (or roller/rtr used on eBay or fb marketplace) so you don't break as much parts and handle better. For those kits I would look at the TLR kits and the tekno sct410.3.
From what I heard the tekno sct410.3 (tekno 4wd sct) has a 1/8 scale based chassis and it is basically indestructible. The TLR SCTE 3.0 is a 4wd sct. The TLR 22SCTE 3.0 is a 2wd sct and based of of the 22 5.0 (2wd buggy)
Another upgrade for the slash, if you still traction roll even when taking corners slow I would get the hot racing sway bar kit. I don't have it on my slash but I seen other people use it and helps with flipping. (The kit does not come with instructions and might need to make modifications to make it fit) I would get a bottle of shock oil and different weights. I wouldn also get different pinion gears and spurs to for tuning and make the car handle better. Lastly I would get extra parts and create a spare parts bin just in case if you break anything.
Also from your videos on yt you are using Traxxas batteries and chargers which are ok. You don't want your battery dead in the middle of the race so I would get 5000ma plus lipos. As for the Traxxas ez peak chargers. They can only charge at 4amps. I would suggest to get a better charger. I would look at dual 6s chargers and that can charge at 10+ amps so you don't have to wait for your battery to charge after each round or heat. Some good chargers are the SkyRC T200(my personal charger), HiTec X2, Hota D6 Pro. These chargers do use different inputs. The SkyRC and Hota use xt60s and the hitec uses 4mm bullets. So I would make or find 4mm bullet to Traxxas lead(for the hitec) or a xt60 to Traxxas (for the others). Speaking of adapters the max 10 G2 uses xt60s so I would make or find xt60 to Traxxas adapter like these:
Adapters